It is desirable to be able to determine at least one parameter of a gemstone automatically or semi-automatically. While a principal purpose of the present invention is to predict the largest polished stone or the most profitable polished stores, that can be obtained from a stone, be it rough, sawn, cleaved, part manufactured (e.g. bruted or blocked) or polished and in need of repair (the word "parameter" as used herein includes such a prediction), the invention, as noted in GB No. 2 081 439 A, is more broadly applicable for determining parameters such as the following (which are exemplary only and not limitative):
in the case of cut (i.e. polished) stones, the make in general (the make is the shape and size of the stone, including the angles and sizes of the parts of the stone as a whole and of the facets);
the profile, in general terms;
the maximum and minimum girdle diameters;
the average or mean girdle diameter;
the table diameter as a percentage of the average or mean girdle diameter;
the crown height as a percentage of the average or mean girdle diameter;
the girdle width (the dimension measured normal to the table);
the pavilion depth;
the pavilion angle;
the angles or lengths of the secondary facets;
the volume;
in the case of bruting, re-measure the bruted stone e.g. to brute further or to determine the correct angle for polishing;
in the case of a rough stone or a sawn half, the largest possible bruted or polished, i.e. brilliant cut, stone of given proportions which can be fitted inside (this can be associated with centering for subsequent bruting or coning, and more details are given in GB No. 2 080 712A)--this can also take account of grain and of unwanted areas such as pique (an inclusion within a stone);
suitable proportions or angles for polished stone;
suitable "swindling", specially if reentrants or other defects are present--"swindling" is a term covering e.g. having the culet off centre, having girdle out of round or tilting the girdle; in the case of a cut stone (particularly a fancy stone, i.e. a stone of irregular shape), the size and shape of the recess in the setting for receiving the stone.